1. Field of the Invention
The present invention relates to a digital cable broadcast receiver, and more particularly, to a method for processing an emergency alert message, and a data structure of the emergency alert message.
2. Discussion of the Related Art
Generally, a digital cable set-top box is required for reception of digital cable broadcast. The digital cable set-top box is connected with a cable head-end, which is a kind of broadcasting station transmitting a digital cable program, to receive an audio/video (A/V) broadcasting program and data broadcast from the cable head-end. At this time, the A/V broadcasting program is received over In-Band among cable frequency bands, and the data broadcast is received over Out-Of-Band (OOB) among the frequency bands. In particular, the cable set-top box can perform two-way communication with the head-end over the OOB.
Broadcast protocols for transmission of channel and broadcasting program guide information may be, for example, Service Information (SI) protocol, and Program and System Information Protocol (PSIP). For the purpose of securing stability in the cable broadcast, SI is transmitted over the OOB, and PSIP information is transmitted over the in-band.
Digital cable broadcast receivers may be, for example, an open cable broadcast receiver adopted in America, a DVB-C broadcast receiver adopted in Europe, and an ISDB-C broadcast receiver adopted in Japan.
In the open cable broadcast receiver, a Point Of Deployment (POD) module with a conditional access (CA) system is separated from the body of a digital cable set-top box in order to prevent copying of high value-added broadcast content and to allow a conditional access thereto. It is thus possible to readily replace a security system with another one and retail the broadcast receiver. Therefore, the digital cable broadcast receiver has the advantage of being capable of being supplied at a low price.
The POD module is inserted in a slot of the digital cable set-top box. In this regard, the POD module is often called a cable card. The POD module and the cable card will hereinafter be used together.
Meanwhile, a cable set-top box-embedded cable broadcast receiver (for example, a cable ready digital TV) has been proposed to enable a retail sale that the open cable system pursues.
This cable broadcast receiver is a digital TV that contains a cable set-top box so that the user can receive and view all terrestrial analog broadcast, terrestrial digital broadcast, cable analog broadcast and cable digital broadcast without using a separate cable set-top box.
A basic convention is defined in the cable broadcast receiver to properly receive and process an emergency alert message if a transmitting stage transmits the emergency alert message to warn of a state of emergency.
That is, if a transmitting stage transmits an emergency alert message at a specific terrestrial frequency or cable frequency, the cable broadcast receiver receives the transmitted emergency alert message. Then, the cable broadcast receiver outputs information regarding a channel change to a specific terrestrial or cable emergency broadcast channel and an emergency alert to the TV viewer in order to effectively provide the emergency alert information to the viewer. At this time, the emergency alert information can be outputted in the form of text and/or audio. For example, when the emergency alert information is in the form of text, it may be slowly scrolled from the upper right to upper left of the screen.
On the other hand, at the time that the emergency alert is ended, the cable broadcast receiver restores the current channel from the emergency broadcast channel to the original channel, viewed by the viewer prior to the emergency broadcast channel, provided that the original channel was compulsorily changed to the emergency broadcast channel.